1. Field
The disclosed embodiments concern a process for high-energy density beam welding two panels mounted plane to plane (transparent) or edge to edge.
2. Brief Description of Related Developments
In many industrial fields, such as the field of aeronautics or automobiles, it is known how to use a high-energy density beam welding process to join two pieces over limited assembly areas. This process of fusion welding some of the materials being assembled makes it possible, because of the localized deposit of energy, to involve only a relatively small volume of melted, thermally affected zones. During the welding operation, the energy concentrated on the panels being welded is intense enough to vaporize the metal directly under the beam, which creates a “keyhole,” also called a capillary. The walls of the capillary are made of fused liquid metal. The metallic bath created and maintained in this way is moved along the pieces being assembled. The fusion metal resolidifies after the beam passes by, ensuring that the pieces are assembled.
FIGS. 1 and 2 of the state of the art show part of the high-energy density welding device in the step of transparent welding of two panels mounted plane to plane (FIG. 1) and a cross section of those two panels connected by the welded joint obtained (FIG. 2).
As can be seen in FIG. 1, to join a top panel 1 to a bottom panel 1, the bottom face 3 of the top panel 1 is mounted to the top face 4 of the bottom panel 2, in the position where it is desired to join the panels 1 and 2. Top means facing the welding device 20, as opposed to bottom. A high-energy density beam 21, such as a laser beam or an electron beam, is applied and moved, for example, longitudinally, in the area of overlap 5 of the panels 1, 2 so as to obtain a welded joint 6 after solidification of the mixture of fused metal of the two panels 1 and 2. As the beam 21 moves, the melting metal located upstream from said beam 21 cools and solidifies to form the welded joint.
As can be seen in FIG. 2, in the case of a capillary opening up, i.e., going through the total thickness of the two panels, the welded joint 7 obtained has a bottom protuberance 8 projecting over the bottom face 9 of the lower panel 2, which can easily be eliminated after the welding step, by sanding, for example. Thickness means the dimension of the panels extending vertically in relation to the plane of the panels. Similarly, a top protuberance 10 projecting from the top face 11 of the upper panel 1 is often obtained, and it can easily be eliminated, once the welding step is finished.
However, the upper protuberance 10, in the axis of the beam 21 is formed, depending on the edges of said metallic bath, so that this upper protuberance 10 is bordered longitudinally by two undercuts 12 or grooves. These undercuts 12 consist of a lack of localized material and extend parallel to the trajectory of the beam 21.
Currently, to eliminate the undercuts obtained on the upper surface of the welded joint, it is known, before the welding step, by a high-energy density process, to machine a reinforcement on the top face of the panel or panels located in the incidence of the beam, so as to locate the undercuts in this reinforcement, which will then be finished.
It is also known from document US2005/0211687 how to increase the volume of the metallic bath by adding metal in the form of wire. However, to do that, it is necessary to use a special mechanism with a motorized wire reel at the head of the beam and to couple it to the speed of advancement of the laser device, which makes the device and using it complex.